Examining-sorting system with cyclic rejection means



0. SILVERMAN EXAMINING-SORTING SYSTEM WITH CYCLIC REJECTION MEANS Filed May 1, 1967 May 20, 1969 I of 2 Sheet Ill-4,1

FIG-4 FIGJ FIG.9.

FIG.5

INVENTOR.

May 20, 1969 D. SILVERMAN 3,

EXAMINING-SORTING SYSTEM WITH CYCLIC REJECTION MEANS Filed May 1. 1967 V Sheet 3 of 2 9 INVENTOR. ns. l2 /fl Z4 United States Patent 3,444,997 EXAMINING-SORTIN G SYSTEM WITH CYCLIC REJECTION MEANS Daniel Silverman, 5969 5. Birmingham,

Tulsa, Okla. 74105 Filed May 1, 1967, Ser. No. 635,106 Int. Cl. B07c 9/00, /00

US. Cl. 209-73 27 Claims ABSTRACT OF THE DISCLOSURE This invention is directed to the provision of object rejection means capable of rapid operation and large rejection force capability.

This is accomplished by providing a high power, high frequency oscillating, pulsating or cyclically moving energy system, a related rejection force generating means, and a coupling means between the two. The coupling means is responsive to the examining or inspection means and is inherently fast-acting so that it can couple the energy means to the force generating means for a single cycle of oscillation or pulsation of the energy means. Control of the geometry between the energy means and the force generating means can determine the fraction of the cycle during which the rejection force will act.

The oscillating system can be mechanical, electromechanical electropneumatic, or pneumatic. The rejection force generating means can be pneumatic or mechanical, and the clutch means can be electromagnetic, fluid-magnetic, fluid-electric, or electric.

This invention relates to the art of sorting of particulate matter such as fruits, grains, seeds, minerals, etc. More particularly it concerns those portions of sorting systems that are concerned with the rejection or removal of a particular object from an array of objects passing through the sorting system.

In the conventional sorting system, means are provided for forming at least one column or linear array of grains or objects. An electro-optical inspection means is provided to examine each of the objects in the column for specific characteristics. When an object has these specific characteristics and is passed before the inspection means, an appropriate signal is sent (through appropriate delay means) to the rejection means. The rejection means acts to remove the particular object from the array.

Most conventional rejection means comprise a source of compressed air, a valve in the air line from the compressor or air storage, and a nozzle through which the air is released to form a stream, beam, or pulse against the object to move it from its original path into a diverging path from which it is caught in an appropriate container.

Since a multiplicity of objects are passing in the array, the time of transit of a single object past the nozzle is quite short and the valve must be fast acting so as to direct the air pulse only to an individual one of the objects. If the valve is too slow in its action, the duration of the air pulse may be long enough so that it acts on a succeeding one or more grains or objects in the array. This is undesirable, and thus an important object of this invention is to provide a rejection means that is much faster in its action than conventional rejection means.

One of the principal problems involved in making a rapidly acting rejection means is that to make such a device fast acting, it must either be small and light, or else a large-power signal must be provided to drive it. Providing means to handle large power requires large size, and so the system becomes self-defeating.

In this invention, I avoid the problem by using a high- Patented May 20, 1969 "ice powered source that is in continuous motion at a high frequency and then, by means of a very light fast-acting clutch or relay means, I couple the rapidly moving power source to the deflection force generating means.

Another object of this invention is to provide a rejection means that can exert a greater rejection force than is now possible with conventional means.

These and other objects, advantages and features of this invention will be more clearly understood from a consideration of the following detailed description taken in conjunction with the attached drawings, in which:

FIGURE 1 is a generalized illustration of a conventional examining-sorting system.

FIGURE 2 is an embodiment of a mechanical oscillating energy means for a rejection system.

FIGURES 3, 4, and 5 show alternate embodiments of driving means for the oscillating system of FIGURE 2.

FIGURES 6, a, b, and c show alternate types of coupling means between the energy means and the rejection force means of FIGURE 2.

FIGURES 7, 7a, 7b, and 8 indicate two forms of pneumatic pulsating energy systems.

FIGURE 9 indicates form of electrical oscillating energy means.

FIGURES 10 and 11 show alternate forms of fluidic amplifiers as pneumatic systems for object rejection.

FIGURE 12 indicates an electrical oscillating energy means coupled to an impulsive pneumatic means, as a rejection means.

In FIGURE 1, I show schematically the apparatus and operation of an examining-sorting system. In general, a linear array of objects 11 is formed at a predetermined velocity along a first path 10, which may be straight or curved. This array may be formed by any one of several means well known in the art. These objects 11 move along the path to successive positions 11a, 11b, 11c, 11d, etc. At position 11a, they are examined by an inspection means such as photoelectric sensor means 12 operating along optical beam 13. The signal from the inspection means 12 goes by means 17 to a rejection control means 14. This examines the signal on 17 to determine whether the object is to be rejected. If so, it sends a control signal over means 18 to the rejection energy means 15. This generates the rejection force which is applied by means 16 to the object 11d to cause it to deviate from the path 10 to a second path 10'.

This invention is primarily concerned with two elements of this system, namely, the rejection energy means 15 and the rejection force generating means 16. These are further illustrated in FIGURE 2.

FIGURE 2 represents a rejection system comprising in schematic form a pulsating or oscillating mechanical rejection energy means and a pneumatic rejection force generating means. This comprises a cantilever beam 21 fastener rigidly to stable mount 22. At the free end of this beam is an operating head 23. By driving means such as those illustrated in FIGURES 3, 4, and 5, the head 23 is made to oscillate or pulsate in the direction of the arrows 42. Closely spaced from the lower portion 32 of the head 23 is a push rod 33 of a valve system 19 into which a fluid is supplied at 37, and out of which a pulse of fluid is provided at 38. There is a coupling means 27 mounted on head 23 such that, on the downward motion of head 23 it is inserted between the head and rod 33 so that the push rod 33 is forced to move downward with the head. Thus, during a portion of single cycle of oscillation or pulsation of 23 the moving head can be made to operate valve 19 to supply a pulse of fluid. While any liquid or gas can be used as the rejection means, for convenience, the apparatus will be illustrated by the use of air as the working fluid.

The head 23 comprises a support 25 for a leaf spring 26 carrying a short vane 27 at its lower end. The spacing between vane 27 and the bottom surface 31 of the head is as small as possible. The vane must be free to move to the left under a small magnetic force from magnet 28 and coil 29. The lower portion 32 of the head is formed in a partial cylindrical tubular form 32, FIGURE 20, that is concentric with the push rod 33, leaving an annular clearance 30.

During a portion of the cycle of oscillation of head 23 the bottom surface 31 of the head is above the top of rod 33 and the vane 27 can be moved to the left to bridge the gap 30, so that as the head 23 moves downward it presses on 27 which presses on 33, forcing the latter downward. The leaf 26 must be of flexible material not only to permit motion of the vane 26 to the left, but also then to permit the vane to be pushed upward into contact with the surface 31. By making the frequency of oscillation of head 23 as high as desired, the length of time that the valve 19 is open can be made as short as desired. Actually, the valve is only open during a portion of the cycle, determined by the spacing 42 between valve assembly 19 and head 23. Adjusting the geometry of energy source 23 and force generating means 19 permits adjustment of the time duration of the rejection force to a small fraction of one cycle.

Of course, the vane 27 must be fast acting also, to move into the operating space in a fraction of a cycle. However, it is a light element and moves only while there is no load on it, so it should be possible to make it move rapidly.

The frequency of oscillation of the system is determined by the mass and stiffness of the system. It can be changed by adding or subtracting mass to head 23, or moving a slider 55 along arm 21 and locking it by means of screw 56.

The energy of the moving system can be quite large, so that once the clutch or vane 27 is operative, this high energy can be applied to the valve system to make it respond rapidly.

The valve system 19 is shown in schematic form and can comprise not only a fluid control, but the push rod 33 can be adapted, as a purely mechanical rejector, to strike and deflect an object to be rejected. In the figure, there is a frame 43 that supports the push rod 33. This is forced by spring 35 and collar 34 to its topmost position. This movement is limited by the valve unit 41 in its seat. This seat opening is in a wall separating chamber 40 from chamber 39. Incoming fluid pressurizes chamber 40, while chamber 39 connected by pipe 38 to the object to be rejected.

This type of an oscillating system is shown by way of example and any translational or rotational spring-mass mechanical system can be used. If the moving mass is to control a valve as in FIGURE 2, a relatively limited movement of head 23 is all that is required. On the other hand, if rejection of an object by mechanical force of a push rod 33 is desired, the amplitude of motion of 23 should be quite large. The total movement of the push rod can, of course, be increased by means of a lever placed between the head and the push rod, as is well known in the art.

In FIGURES 3, 4, and 5, I show additional schematic drawings of drive systems for the oscillating system. In FIGURE 3, I show a rod 51 attached to arm 21. This rod supports coil 52 with leads 53 in an annular air gap in magnetic structure 54. By applying an A-C current to coil 52, of the proper frequency (timed to the natural frequency of the mechanical system) a resonance is obtained and a high amplitude of motion of the head 23 is possible.

In FIGURE 4, a different magnet system 61 with coil 62 is mounted to attract the arm 21, which should be of magnetic material. On the opposite side of the arm is a conducting leaf spring 64 mounted to the arm at 65 and carrying contact 66. This makes electrical connection with a stationary lead 67 mounted on insulator 68 on stationary mount 69. A closed circuit between coil 62, battery 63, contacts 66, 67, and switch 73 makes this system a self-excited oscillator (like the conventional buzzer) at the frequency set by the mechanical system.

In FIGURE 5, I show a rotating system 76 rotating about shaft 78 mounted on arm 21. This system carries an unbalanced weight 77. When rotated by motor 79, also mounted on arm 21, it generates a transverse oscillating force on the arm 21. By controlling the speed of the motor by means not shown but well known, the pulsating force due to the rotating mass can be tuned to the natural frequency of the oscillating system.

In FIGURE 2, I showed a single simple electromagnetic vane as a one-way-acting driving clutch between the high energy, pulsating, energy system and the lightweight rejection force control means. In FIGURE 6, I show, as examples of other clutch means, a magnetic-mechanical clutch (FIGURE 6a), a magnetic-fluid clutch (FIGURE 6b), and an electrostatic-fluid clutch (FIGURE 60).

In FIGURE 6a, the rod 91 is an extension of the moving head system 23. It is formed into a fork with spaced flexible arms 92, 93. A magnetizing coil 94 is mounted to be stationary and to surround and clear the arm 93 about which it is wound. Therod 95 is an extension of push rod 33 of FIGURE 2. It slides freely between the arms 92, 93, as they oscillate in accordance with arrows 97. When the coil 94 is energized, the magnetic flux 96 is set up, which pulls the flexible arms '92, 93, together to clamp rod 95 and carry it with the rod 91. Stopping current to coil 94 releases the arms 92, 93, and the friction drive on rod 95 is removed.

In FIGURE 6b, I show the same rod 91, and forked arms 92, 93. These need not be flexible. Again they straddle (with proper clearance) the rod 95. In the gaps is a magnetic oil. By the application of a magnetic field illustrated as magnet poles, N, S, by a coil and current system not shown, there is a clamping force between the fluid and the arms 92, 93, and rod 95. This is a well known phenomenon and has been utilized in magneto-electric clutches for many years. Releasing the magnetic field, releases the driving action and frees the rod 95.

In FIGURE 60, I show a system similar to that in FIGURE 6b, except here I use an electrostatic oil as the clutch element. This is also a well known phenomenon since 1947, when it was developed by W. M. Winslow. This is known as the Winslow Etfect. Patent rights are held by Warner Electric Brake and Clutch Company, Beloit, Wis. When an electric potential is supplied by battery and switch 106 between arms 92, 93, and rod 95, the treated oil 107 will become very viscous and prevent relative movement of rod 91 and rod 95. Since these electromagnetic and electrostatic oils are well known in the art, there is no need for further description of these phenomena. Thus, by magnetic, fluid-magnetic, and fluid-electric systems the moving head system 23 can be coupled to the push rod 33 for short controllable periods.

In FIGURE 7, I show a pneumatic oscillating system. This comprises a rigid wall member with a transverse central opening 120. On one side is mounted a flexible cone or diaphragm means, like a loud speaker cone 116. Mounted on the end of this cone is a driving coil 117 placed in the annulus of a radial field magnet 119. Applying an A-C current to coil leads 118 causes the coil to oscillate in and out of the gap, causing the cone to expand and contract, thus forcing air to be drawn into and expelled from the chamber 125 formed by the cone and the wall 115. This chamber 125 and conduit 120 form an acoustical resonating system of the Helmholtz type. These can be designed by well known means to have a desired natural frequency. Or the volume or conduit dimensions can be adjusted to modify the natural frequency to a desired value. Driving the coil 107 at this resonant frequency will provide a high amplitude of oscillation and periodic pulses of air out of the opening 120 along axis 126 to the object to be rejected. It is well known with this type of pneumatic oscillating system that when air is drawn into the opening 120 it comes from all directions 127, 128, 129, etc., FIGURE 7a. But when air is expelled, the air moves out as a column 127', 128', 129', etc., all more or less in the same direction as in FIG- URE 7b. Thus this system provides a more or less unidirectional pulsating fluid flow which can be used to reject an object placed along the axis 126.

The pulses of air 127, 128, 129, will be larger for this ocsillating system than would be provided by a single transient operation of the coil and cone with a current of the same magnitude. However, it is necessary to block the pulses of air except when a rejection is required. This is accomplished by a reed 121 which is set with vane portion 114 to block off the opening. The reed is mounted at 122 and can be attracted by magnet 145 and coil 146 so as to clear the opening and allow a pulse of air to pass.

In FIGURE 8, I show another embodiment of an air pulse generator. This comprises a rotating disc 130, rotating about axis 131 and driven by motor 133, through means 132 in the direction 136. There is an axial opening 134 which leads to radial passages 135 within the disc, preferably equally spaced around the circumference. Air is supplied to the opening 134 and flows out of each of the radial passages. This disc is mounted inside of a cylindrical housing 147 that has a very narrow annular air space 148 between the disc and the housing. The housing has an opening 149. The annular spacing 148 is so small that effectively, no air flows out of 135 except through the opening 149, sequentially as each of the passages 135 sweep across the opening. Inset into the contour of the housing and opposite the opening 149 is a mask 140 with matching opening 141. The opening 149 has a tapered portion 138. The opening 138 terminates in a longitudinal orifice 139 to form the column of air. Again, a reed 142 with vane 144 is mounted at 143. It has a magnet 145 and coil 146 to pull the reed aside to permit the vane to unblock the orifice 139 to allow the beam to project along axis 150 to the object to be rejected.

Pulses of air will appear at 139 each time a radial passage 135 comes opposite the opening 149. The duration of the pulse is equal to the travel time of the passage 135 across the opening 149. This time can be reduced by sliding mask 140 around until it coves part of the opening 149. Thus the duration of the rejection pulse can be made as small as desired.

The high precision of time control of the vane 144 is not required since it can start to move as soon as the previous passage 135 has passed the opening 149 and can close just before the succeeding one comes to the opening. The precision of timing of the pulses is dependent on the constant speed drive of motor 133. This speed can be coordinated with the flow of objects past the orifice through drive connections between motor 133 and the motor driving the means for creating the moving array of objects.

Of course, it is possible to stop the rotation of disc 130 and have a constant air pressure in opening 149 and a constant stream of air through orifice 139. However, as indicated above, this requires that the deflecting vane be precisely and rapidly controlled, which is very difficult to accomplish, so the preferred system is indicated in FIGURE 8, where the repetition rate and duration of the pulses is controlled by the rotating disc, and the on-ofl control is accomplished by the vane 144.

In FIGURE 9, I show an electrical oscillating circuit in schematic form comprising a source of A-C power of a desired frequency 160, a parallel resonating circuit comprising capacitance 163 and inductance 164, and a shunt circuit comprising switch 165 and solenoid valve coil 166, which controls an air supply under pressure, not shown. At resonance, in the oscillating loop of inductance and capacitance the current flow as indicated by the arrow is larger than the current supplied by the source E. Thus, when the switch 165 is closed, the source E passes current through the valve coil and the energy stored in the oscillating loop is supplied in the form of a high current, and the valve operating coil 166 receives a much larger momentary power than could be supplied by the source E without the energy storage in the oscillating circuit 163, 164. The switch 165 can conveniently be a grid controlled tube such as an ignitron (or the equivalent solid state controlled rectifier) that can be started by grid control and stopped by the current passing through zero. In place of the valve 166 it is possible to use drive to the coil 118 of FIGURE 7 by connecting it across the inductance 164. Thus the large pulse of current from inductance 164 can be used to drive a cone or diaphragm.

In FIGURE 10, I show another type of oscillating or pulsating system that can be used as an energy source for rejection force generating means. These are fluidic systems. In the figure, represents an oscillating unit and 161 represents a coupling or switching unit. As will. be described below, the two units can be combined into a single unit if desired, and other types of switching units can be used with the oscillating unit, and vice-versa, the switching unit can be used without the oscillating unit, and so on.

The fiuidic unit 160 is a fluid amplifier. This is a relatively new art and is described in a number of publications, such as the book, Fluidics, edited by E. F. Humphrey and D. H. Tarumoto, and published in 1965 by Fluid Amplifier Associates Inc. of Boston, Mass. It is a five-terminal device, comprising a chamber 163 with an input 162, two outputs 164, 165, and two control inputs 166, 167. With no control, the incoming air 162 divides equally between the two output legs 164, 165. However, if air is introduced into control input 166, such as by conduit 168 from the input 162, the main air stream will be diverted from 162 to 165, and no air will exit through 164. However, the air exiting from 165 can be carried by conduit 169 to control input 167. Then if the stream of air entering 167 is greater than that entering 166, the stream of air from 162 will switch from leg 165 to leg 164 and will flow out of 164. However, as soon as this happens, the control air inflow at 167 stops and the air flow in from 166 again switches the stream back to 165, and so on. This makes for a self-sustained oscillation as long as air is supplied at 162.

Air pulses are provided at 164 at the frequency of oscillation of the system. This frequency is controlled by the acoustical constants of the leg 165, conduit 169, and control 167. Any additional volume, such as 183, will act as storage (like a capacitor in an electrical system) and lower oscillation frequency. The frequency is also controled by the velocity of sound in air, or the time it takes an acoustical pulse to travel from 165 through 169 to 167.

The input to the second unit 161, which is a switching unit, is now a pulsating stream of air. This unit, like 160, has an input 173, two outputs 171, 172, and two controls 174, 176. Part of the input air from 173 is bled 011 by 175 to the control input 174. This insures that the air entering 173 is diverted to leg 172 to the atmosphere. However, in control inlet 176, I have a chamber 177 into which is sealed a pair of electrodes 178. These are connected through switch 179 to capacitor 180 which is kept charged by D.-C. source E, 182 through resistor 181. When the switch 179 is closed, a spark forms between the electrodes 178 and the condenser discharges through the spark, generating heat which generates pressure in the air in 177 forming a pulse of air through control 176 into chamber 170. This momentarily diverts the stream of air from leg 172 to leg 171, where it is projected along axis 184 to the object to be rejected. As soon as the pulse entering 173 and diverted to 171 is finished, there is a short period in which no air flows into 173. In the next oscillation of 160 the air is again diverted to leg 172, and so on. In this type of system in which a pulsating air stream is controlled, the control signal (such as the switch 179, which can, of course, be a solid state device) is synchronized with the oscillation of 160 (by well known means such as pressure sensors) so that the switch is closed during the half cycle when air is flowing into 173. Of course, a mechanical switch, vane, or valve can be substituted for spark chamber 177. Since these are inherently slower operating devices than the spark gap, they can be set up during the half cycle when air is not flowing into 173. Then as air flow starts it will be sent directly to 171.

This is shown in FIGURE 11 in which the unit 200 is similar to 160, except that there is a control 201 in the bypass 205 from leg 221 to control 218. This control is shown schematically as a flexible tube 202 in a chamber 206 which can be moved physically from position 202 where it discharges air from 221 to 204 and to the atmosphere, to position 203 (shown dotted), where it dis charges air from 221 to 218 and so diverts the main air stream to leg 220 and to axis 222 to the object to be rejected. To cause the pulse at the tube 202 is momentarily moved to position 203 where the air in 221 is diverted to 205 and 218. The tube can be moved by electromagnetic means such as rod 207, coil 208, and magnet 209. Tube 203 must be returned to position 202 promptly to avoid a succession of pulses at 220. If unit 200 is substituted for 161, then the tube 202 is moved over in the quiet half cycle, left at 203 during the operative half cycle of air in 164, 173, and then returned to position 202 after the pulse of air is stopped. Here, as in the system described above, the duration of the pulses is controlled by the oscillating system and the speed requirement on the control or clutch means is reduced. It will be clear that the choice of the flexible tube control is for example only, and other means such as the vanes of FIGURES 7 and 8, could be used to control the flow of air into 218.

The spark electrodes and circuit shown operating in the chamber 177 of FIGURE 10 could, of course, be used to generate a pulse of air directly against the object to be rejected. However, in FIGURE 10, it is shown operating in the control inlet of the fiuidic amplifier 161. Thus, its output can be magnified by the amplification ratio of the fluidic amplifier, which may be as much as 10 or more. Thus the electrical requirements are reduced by this factor when used in the manner shown in FIGURE 10. Also, fiuidic unit 161 can be used without oscillator 160. That is, a constant supply of air can be supplied at 173, which is normally diverted to leg 172 by control 174. Then on closing switch 179, the stream is diverted to leg 171 for as long as the pulse of air from 177 continues. The magnitude and time duration of this pulse, and thus of the stream from 171 along axis 184 can be controlled by changing the magnitude of energy stored in capacitor 180.

In FIGURE 9, I show an electrical oscillating circuit which is used as a storage means to supply momentary pulses of power to a rejection force means, such as the air control valve whose coil 166 is connected into the circuit. In a similar manner, an electrical resonating circuit can be used to provide a high value of A.C. voltage to be applied to the spark gap when the switch is closed. This is shown schematically in FIGURE 12, in which a series resonating inductance and capacitance are used to form the resonating circuit. Alternating current source 245 supplies current to the series connected capacitance 246 and inductance 247. Across the inductance is connected a switch 248 and the spark gap 249 encased in a spark chamber 250 having a single orifice 251. When the frequency of the source E is tuned to the resonance frequency of the inductance and capacitance, a very large current flows and a very high voltage appears across the inductance and the capacitance, very much higher than the supply voltage 245. When the switch 248 is closed, the high voltage across the inductance breaks down the spark gap and a large current flows through the spark causing a pulse of air to be expelled from the orifice 251 and along the axis 252 to the object to be rejected. Of course, instead of supplying the resonating circuit 246, 247, with AC. power, a self-contained oscillating circuit (including the elements 246, 247) can be set up, as is well known in the art.

I have shown a number of embodiments of the invention illustrated with the attached figures. These are shown by way of example and one skilled in the art may devise other embodiments or combinations of embodiments which will similarly illustrate the principles of this invention. All of these embodiments are to be considered part of this invention, the scope of which is to be determined from the scope of the appended claims.

I claim:

1. In a sorting system which includes means to form at least one linear array of objects following a predetermined first path, inspection means, rejection control means responsive to said inspection means, and rejection means responsive to said rejection control means, the improvement comprising,

cylically varying energy means,

rejection force generating means, and

energy control means comprising control means between said energy means and said rejection force generating means, said energy control means responsive to said rejection control means,

whereby, when said energy control means is activated by said rejection control means, said rejection force generating means is coupled to and driven by said energy means.

2. Apparatus as in claim 1 in which said energy means comprises a pulsating energy means.

3. Apparatus as in claim 1 in which said energy means comprises an oscillating energy means.

4. Apparatus as in claim 1 in which said energy means comprises a moving mechanical means.

5. Apparatus as in claim 4 in which said moving mechanical means comprises a compliance-mass system.

6. Apparatus as in claim 1 in which said energy means comprises a moving fluid means.

7. Apparatus as in claim 1 in which said energy means comprises an electrical oscillating system.

8. Apparatus as in claim 7 including electromagnetic control of pneumatic means driven by said electrical oscillating means.

9. Apparatus as in claim 8 in which said electromagnet control comprises valve means.

10. Apparatus as in claim 8 in which said electromagnetic control comprises diaphragm means.

11. Apparatus as in claim 7 including spark chamber means to create a pneumatic pulse.

12. Apparatus as in claim 1 in which said energy control means is electromechanical.

13. Apparatus as in claim 1 in which said energy ontrol means is electromagnetic.

14. Apparatus as in claim 1 in which said energy control means is electric.

15. Apparatus as in claim 1 in which said rejection force generating means comprises pneumatic valve means.

16. Apparatus as in claim 1 in which said rejection force generating means comprises pneumatic deflection means.

17. Apparatus as in claim 1 including means to vary a parameter between said energy means and said rejection force generating means, whereby the fraction of the pulsation period during which said rejection force generating means is activated can be varied.

18. Apparatus as inclaim 17 in which said energy means is mechanical and said parameter is the spacing between said energy means and said rejection force generating means.

19. Apparatus as in claim 1 including electro-pneumatic means to generate pneumatic pulsations.

20. Apparatus as in claim 1 including rotating pneumatic means to generate pneumatic pulsations.

21. Apparatus as in claim 1 including fluidic amplifier means.

22. Apparatus as in claim 1 including fluidic oscillating means to generate pneumatic pulsations.

23. Apparatus as in claim 1 including a plurality of rejection force generating means each adapted to be coupled to said energy means by one of a plurality of energy control means.

24. Apparatus as in claim 1 including fluidic amplifier means and electric means to switch control of the fluid stream in said fluidic amplifier means.

25. Apparatus as in claim 24 in which said electric means comprises spark means.

26. Apparatus as in claim 1 including fluidic amplifier means and electromagnetic means to switch control of the fiuid stream in said fluidic amplifier means.

27. Apparatus as in claim 1 including fluidic amplifier means and vane means to switch control of the fluid stream in said fluidic amplifier means.

U.S. Cl. X.R. 20974 

